This invention relates to fluid collection devices and more particularly to vacuum loss indicating means for a body fluid collection device.
A body fluid collecting device, such as a blood collection tube, has a stopper at one end for maintaining a negative pressure within the tube. The stopper is adapted to be pierced by one end of a double ended needle cannula to effect communication between the negative pressure within the tube and a body vessel that has been pierced by the other end of the needle for drawing blood from the vessel into the tube for test purposes. Should blood fail to be drawn into the tube due to a loss of vacuum in the tube after the needle has been inserted into the patient and the stopper penetrated by the needle, the person withdrawing the blood might assume that the vessel has not been properly penetrated and may make one or more penetrations causing damage to the vessel and surrounding tissue before substituting a new tube. It is therefore desirable to provide some means of indicating, such as by a visual indication, that a negative pressure or partial vacuum does exist in the collection tube before an attempt to use the tube is made.
In U.S. Pat. No. 3,890,955, a vacuum loss indicator is disposed within a collection tube to provide a visual indication that there is or is not a negative pressure in the tube before it is put to use. In this patent, an indicator, such as hemoglobin, is disposed within the tube. Other indicators mentioned include other chemicals, a feather and a ball which will drop at different speeds depending on the air content of the tube, and an object having a pair of vanes and which spins like a helicopter blade in the presence of air in the tube. The disadvantages of such arrangements are that the material collected, such as blood, comes in contact with the indicator and, in some cases, may affect the outcome of the analysis of the blood, or may otherwise contaminate the blood drawn into the tube. In some cases, the type of indicator means limits the type of material that can be satisfactorily drawn into the tube or the type of indicating means may be limited by the material to be drawn into the tube.